The covering of landfills is a practice required by regulation in many jurisdictions. For example, it is often required that the daily fill of garbage be covered at the end of the day, or that the landfill be covered when it is not in operation. It is known in the industry to lay strips of film, such as degradable polyethylene, in a side-by-side or overlapping arrangement to cover the landfill, and to place ballast (anchoring material) such as dirt on the film to hold it in place. In the present disclosure, the term “film” includes membranes, textiles, sheathing materials, and similar sheet-like material suitable as a ground cover. The ground area that requires regular covering in a landfill may be very large, and machines have been developed to apply strips of film to cover such areas.
WO 2012/061918 (Kozak) and U.S. Pat. No. 9,440,268(Kozak et al.), which are incorporated herein by reference, disclose a tracked, self-propelled machine for laying a film and depositing ballast on it to cover a landfill. A roll of film is supported at the back of the machine for unwinding onto the ground surface as the machine moves forward, and ballast is released from the back of a box on the machine and is deposited on the laid film.
In prior art machines of this type, the ballast is moved to the back of the ballast box for release onto the laid film by means of a hydraulic chain floor, which has spaced-apart pairs of chains connected to bars extending transversely to the longitudinal axis of the machine, to engage and move the ballast. However, the ballast available at landfill sites often includes large rocks and pieces of concrete. When such material is loaded into the box, for example by being dropped from the bucket of a front-end loader, the chains are liable to be damaged or broken, rendering the chain floor inoperable.
There is a need for a film-laying machine which can use ballast of the type that can damage chain floors, and ballast of significantly different densities.